/*
 * Copyright (C) 2005 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.reflect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;

/**
 * Static utilities relating to Java reflection.
 *
 * @since 12.0
 */
@Beta
@ElementTypesAreNonnullByDefault
public final class Reflection
{

    /**
     * Returns the package name of {@code clazz} according to the Java Language Specification (section
     * 6.7). Unlike {@link Class#getPackage}, this method only parses the class name, without
     * attempting to define the {@link Package} and hence load files.
     */
    public static String getPackageName(Class<?> clazz)
    {
        return getPackageName(clazz.getName());
    }

    /**
     * Returns the package name of {@code classFullName} according to the Java Language Specification
     * (section 6.7). Unlike {@link Class#getPackage}, this method only parses the class name, without
     * attempting to define the {@link Package} and hence load files.
     */
    public static String getPackageName(String classFullName)
    {
        int lastDot = classFullName.lastIndexOf('.');
        return (lastDot < 0) ? "" : classFullName.substring(0, lastDot);
    }

    /**
     * Ensures that the given classes are initialized, as described in <a
     * href="http://java.sun.com/docs/books/jls/third_edition/html/execution.html#12.4.2">JLS Section
     * 12.4.2</a>.
     *
     * <p>WARNING: Normally it's a smell if a class needs to be explicitly initialized, because static
     * state hurts system maintainability and testability. In cases when you have no choice while
     * inter-operating with a legacy framework, this method helps to keep the code less ugly.
     *
     * @throws ExceptionInInitializerError if an exception is thrown during initialization of a class
     */
    public static void initialize(Class<?>... classes)
    {
        for (Class<?> clazz : classes)
        {
            try
            {
                Class.forName(clazz.getName(), true, clazz.getClassLoader());
            }
            catch (ClassNotFoundException e)
            {
                throw new AssertionError(e);
            }
        }
    }

    /**
     * Returns a proxy instance that implements {@code interfaceType} by dispatching method
     * invocations to {@code handler}. The class loader of {@code interfaceType} will be used to
     * define the proxy class. To implement multiple interfaces or specify a class loader, use {@link
     * Proxy#newProxyInstance}.
     *
     * @throws IllegalArgumentException if {@code interfaceType} does not specify the type of a Java
     *                                  interface
     */
    public static <T> T newProxy(Class<T> interfaceType, InvocationHandler handler)
    {
        checkNotNull(handler);
        checkArgument(interfaceType.isInterface(), "%s is not an interface", interfaceType);
        Object object =
                Proxy.newProxyInstance(
                        interfaceType.getClassLoader(), new Class<?>[]{interfaceType}, handler);
        return interfaceType.cast(object);
    }

    private Reflection()
    {
    }
}
